Non-contact, capacitive, portable presence sensing

ABSTRACT

A movement-sensitive capacitive sensor includes a first conductive element and a second conductive element positioned adjacent to the first conductive element. The sensor also includes a first protective insulator and a second protective insulator sealed to the first protective insulator with the first conductive element and the second conductive element positioned between the first protective insulator and the second protective insulator. The sensor further includes a circuit configured to calculate, over time while a person is occupying the movement-sensitive capacitive sensor and moving while occupying the movement-sensitive capacitive sensor, capacitance values between the first conductive element and the second conductive element. The circuit also is configured to determine an occupancy state of the movement-sensitive capacitive sensor based on the calculated capacitance values, determine movement-sensitive measurements based on the calculated capacitance values, and transmit output based on the determined occupancy state and the determined movement-sensitive measurements.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation (and claims the benefit of priorityunder 35 USC 120) of U.S. application Ser. No. 13/828,847, filed Mar.14, 2013, now allowed, which claims the benefit of U.S. ProvisionalApplication Ser. No. 61/728,008, filed Nov. 19, 2012. Both of theseprior applications are incorporated by reference in their entirety.

TECHNICAL FIELD

This disclosure relates to non-contact, capacitive, portable presencesensing.

BACKGROUND

Recent technological advancements have facilitated the detection ofoccupancy on human support surfaces such as beds, cushioned seats, andnon-cushioned seats (e.g., chairs and sofas) via sensors placed directlyabove or below the support surface (e.g., cushion or mattress). Morespecifically, a binary occupancy sensor produces a distinct output whena support surface is either occupied or unoccupied. Beyond supportsurface detection, a broad application space exists for human-centricbinary occupancy sensing, ranging from safety to wellness assessment.For example, bed and seat occupancy sensors can be utilized to measureand assess sedentary behavior (e.g., time spent in bed or seat) and fallrisk (e.g., bed entries and exits, time spent away from bed, etc.).Occupancy can be measured with electrically conductive contacts (e.g.,electrical contact created when occupied) or more complex sensingmechanics (e.g., resistive, load cell, pressure, etc.) filtered toproduce binary output.

More complex sensing elements can also measure small variations inmovement and provide corresponding variable output. Such sensors aretypically placed in close proximity the sensed body. Combined withsophisticated signal filtering and processing, diverse applications ofsuch movement-sensitive sensors range from sleep quality measurement todetection of breathing rate, heart rate, and sleep apnea.

SUMMARY

Techniques are described for non-contact, capacitive, portable presencesensing.

Implementations of the described techniques may include hardware, amethod or process implemented at least partially in hardware, or acomputer-readable storage medium encoded with executable instructionsthat, when executed by a processor, perform operations.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features will beapparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIGS. 1 and 2 are diagrams that illustrate example capacitive sensors.

FIG. 3 is a diagram that illustrates the capacitive sensing principle.

FIG. 4 is a diagram that illustrates an example interlocking comb-toothconductive element pattern.

FIG. 5 is a diagram that illustrates an example cross-bar arrayconductive element pattern.

FIG. 6 is a diagram that illustrates an example circuit.

FIG. 7 is a view that illustrates an external appearance of an examplecapacitive sensor.

FIG. 8 is a flow chart illustrating an example process for occupancysensing.

FIG. 9 illustrates an example signal corresponding to a transition to,and back from, an unoccupied state.

FIG. 10 illustrates an example state diagram that shows transitions froman occupied state to an unoccupied state and transitions necessary forauto-correction of state.

DETAILED DESCRIPTION

Techniques are described for non-contact, capacitive, portable bed andseat presence sensing. In some implementations, a sensor has adjacentcapacitive sensing elements, combined with in-sensor computationalprocessing, that allows for both binary occupancy detection andmovement-sensitive variable measurement. In these implementations, thesensor may have a flexible and fabric structure that allows it to beutilized as an external sensor on existing beds and seats (e.g., abovethe surface and near the sensed body) or integrated into bed or seatconstructions (e.g., within the bed or seat) without being felt by theuser. The sensor may be inexpensive, hygienic, comfortable, accurate,precise, and/or portable (e.g., easily moved between applicationenvironments and support surfaces).

FIG. 1 illustrates an example capacitive sensor 100. The capacitivesensor 100 is a non-contact capacitive sensor that includes conductiveelements 110 and 120. A top protective insulator 140 and a bottomprotective insulator 150 are sealed together to encase the conductiveelements 110 and 120. The top protective insulator 140 and the bottomprotective insulator 150 may include anti-microbial surfaces, non-slipsurfaces, or simple fabrics. The capacitive sensor 100 also includes acomputational circuit 160 attached via wires and conductive attachmentpoints 170 to the conductive elements 110 and 120. The conductiveattachment points 170 may include a conductive fastener, such asconductive Velcro, that provides a direct connection between the circuit160 and the conductive elements 110 and 120.

FIG. 2 illustrates another example capacitive sensor 200. In thecapacitive sensor 200, the conductive elements 110 and 120 are printedon or adhered to the bottom protective insulator 150. In otherimplementations, the conductive elements 110 and 120 may be printed onor adhered to the top protective insulator 140. The conductive elements110 and 120 may be conductive ink printed on the top protectiveinsulator 140 or the bottom protective insulator 150.

As shown in FIG. 3, in the capacitive sensor 100 as shown in FIG. 1 andthe capacitive sensor 200 as shown in FIG. 2, the conductive elements110 and 120 are placed adjacent to one another to define a capacitiveelement influenced by presence of a sensed body within close proximity.When a sensed object 310, such as a human body, is near the conductiveelements 110 and 120, electric field lines 320 between the conductiveelements are disrupted, and the charge distribution on the conductiveelements 110 and 120 changes. The left portion of FIG. 3 shows theelectric field lines 320 undisrupted and the right portion of FIG. 3shows the electric field lines 320 disrupted by the sensed object 310.The circuit 160 detects the change in charge distribution on theconductive elements 110 and 120 to sense the presence of the sensedobject 310.

In some examples, the conductive elements 110 and 120 may be patternedto increase sensitivity to movement of the sensed body and/or toincrease sensitivity of sensing position of the sensed body relative tothe sensor. FIG. 4 illustrates an example interlocking comb-toothconductive element pattern for the conductive elements 110 and 120. Theinterlocking comb-tooth conductive element pattern may be used toincrease sensitivity to movement on the surface of the sensor. In thisexample, the two conductive elements 110 and 120 are shaped to increasethe detection area and/or to identify the area of the body in contactwith the sensor.

FIG. 5 illustrates an example cross-bar array conductive element patternfor the conductive elements 110 and 120. The cross-bar array may be usedto identify position of the sensed body relative to the sensing surface.In this example, a multiplicity of conductive elements provides a gridfrom which adjacent elements may be measured to determine position inthe sensing plane (e.g., two-axes of position). The grid may include aseparate conductive element for each row and each column such thatchanges in charge distribution on adjacent conductive elements may bemeasured to identify a two-dimensional location at each point where thebody contacts or is positioned over the sensor.

FIG. 6 illustrates an example of the circuit 160. As shown in FIG. 6,the circuit 160 includes digital and analog components that convertcapacitance to a digital value. For instance, the circuit 160 includes afirst sensing element input 610 that is connected to the conductiveelement 110 and a second sensing element input 620 that is connected tothe conductive element 120. The circuit 160 also includes apre-processing circuit 630 and a processor 640. In some implementations,the pre-processing circuit 630 may also be integrated into the processor640. The pre-processing circuit 630 receives input from the firstsensing element input 610 and from the second sensing element input 620and performs pre-processing on the received inputs. The pre-processingcircuit 630 provides results of pre-processing to the processor 640. Thepre-processing circuit 630 and processor 640 digitally process thesignals for the conductive elements to detect occupancy or quantifysmall changes in movement of the sensed body. For example, thepre-processing circuit 630 may convert sensed capacitance between theconductive elements 110 and 120 into an oscillating signal of varyingfrequency at digital logic levels.

Moreover, the circuit 160 may include a wireless radio 650 thattransmits capacitance, occupancy, or small changes in the sensed body'smovement to a remote location (e.g., a base station, a mobile device, awireless router, etc.). The circuit 160 also may include localmemory/storage 660 that stores capacitance, occupancy, or movement data.The memory/storage 660 may temporarily store capacitance or occupancydata prior to transmission by the wireless radio 650 to a remotelocation (e.g., a base station, a mobile device, a wireless router,etc.). Further, the circuit 160 may include input/output and userinterface components 670 (e.g., a button and a light-emitting diode(LED)) to facilitate user interaction. User interaction may be necessaryfor sensor calibration prior to use. For example, the circuit 160 mayreceive user input that initiates a calibration process and thatindicates that no user is present on the sensing surface. In thisexample, the circuit 160 may measure the capacitance in the unoccupiedstate based on receiving the user input to calibrate the sensor.Calibration may promote higher accuracy measurement.

To measure capacitance, the circuit 160 may employ various processes.For example, the circuit 160 may utilize a Schmitt-trigger along with aresistor to oscillate between digital logic levels (“0” and “1”) at afrequency directly related to the sensed capacitance and the “RC timeconstant” created with the added resistance. In this example, theoscillating signal serves as a clock source for a counter. Thedifference in counter value is measured over a known period of time(obtained from another time source), and the number in the counterdirectly corresponds to the sensed capacitance.

In another example, the circuit 160 measures capacitance by introducinga transient input in voltage and/or current and then measuring theresponse to the transient input with respect to time. In this example,the circuit 160 calculates capacitance based on the measured responseand time. These processes, among others, may be used to sense minutechanges in capacitance with small, inexpensive, and power efficientcircuitry. The power efficiency may allow the circuit 160 to beexternally or battery powered.

FIG. 7 illustrates an example implementation of the capacitive sensor100 with a top view being shown. As shown in the top view, the topprotective insulator 140 defines an external top surface of thecapacitive sensor 100. The circuit 160 is positioned within a circuitbox, which is external to the sensor protective insulators 140 and 150.Wires or a conductive fastener connect the circuit 160 to the conductiveelement 110 and the conductive element 120, which are positioned betweenand covered by the top protective insulator 140 and the bottomprotective insulator 150.

FIG. 8 illustrates an example process 800 for occupancy sensing. Theoperations of the example process 800 are described generally as beingperformed by the circuit 160. In some implementations, operations of theexample process 800 may be performed by one or more processors includedin one or more electronic devices. As shown in FIG. 8, the circuit 160provides computational capabilities to calibrate the sensor (810),calculate capacitance (820), determine occupancy state or othermovement-sensitive measures (830), determine operational state (840),cache or store data (850), and transmit data off of the sensor (e.g.,wirelessly) (860).

The circuit 160 calibrates the sensor 100 (810). The sensor 100 may becalibrated manually or automatically. To calibrate the sensor 100manually, the circuit 160 determines that the sensor 100 is unoccupiedbased on receiving user input (e.g., a press of a button on thecomputational circuit device) or based on receiving, from anotherelectronic device, a signal that initiates a calibration process (e.g.,a wirelessly received command). Upon initiation of the calibrationprocess, the circuit 160 determines a capacitance measured by thecircuit 160 in the unoccupied state and uses the determined capacitanceas a baseline measurement for calibrating the sensor 100. The circuit160 may set a threshold between the occupied and unoccupied states byadding an offset value, δ, from the calibrated value. The offset value,δ, reduces the likelihood of minor environmental changes and electricalnoise causing unwanted state transitions. Sensor calibration may beperformed periodically, as the unoccupied capacitance value may changeover time.

In some implementations, the circuit 160 may automatically performperiodic calibration without requiring user input or an outside signalto initiate the calibration. To calibrate the sensor automatically, thecircuit 160 determines the unoccupied state and occupied state based onlarge rapid changes in the calculated capacitance values. To achievethis automatic calibration, the circuit 160 performs a process to managethese state changes.

An example of an automatic calibration process is explained hereafter.FIG. 9 illustrates and annotates relevant variables for an examplesignal corresponding to a transition to, and back from, an unoccupiedstate. Sampled values corresponding to the current state are averagedover a multiplicity of samples (denoted as T) to subtract small changesin the applied dielectric, as well as noise from both the electrical andmechanical systems. Therefore, at any time t, the process has anestimate of the average acquired signal in the current state (S_(AVG)).Another variable, δ, is defined as the amount of signal change requiredfor activation or deactivation. Activation and deactivation thresholds Aand D are set as described in Eq. 1 and Eq. 2 (below). Consequently, theactivation and deactivation thresholds are updated on the time interval,T, to compensate for small changes in the applied dielectric, andtherefore, sensed capacitance corresponding to the unoccupied oroccupied state.A=S _(AVG)−δ   Eq. 1: Activation Threshold EquationD=S _(AVG)+δ   Eq. 2: Deactivation Threshold Equation

Without complete certainty of being in the correct state at any giventime, it is possible that either an activation threshold or deactivationthreshold is reached at any point in time, regardless of the currentstate. Accordingly, the approach for automatic calibration allows forauto-correction if the previous state was incorrect. FIG. 10 illustratesan example State Diagram 1000 that shows the transitions from theoccupied state to the unoccupied state and the transitions necessary forauto-correction of state. If the system is incorrectly in the occupiedstate, then a capacitance change of −δ results in no state change andthe resetting of S_(avg) (the converse is true for the unoccupiedstate). The uncertainty of being in the incorrect state may be reducedby setting the offset variable, δ, to a large enough value so that itdoes not cause transitions based on minor environmental changes andelectrical noise. Nonetheless, this offset variable, δ, needs to besmall enough to accurately detect the presence of the desired object(e.g., the human body).

Other processes of automatic calibration also may be employed withoutthe use of manual or command-initiated device input. For example,capacitance values may be statistically profiled and unsupervisedmachine learning processes may be implemented to classify occupancystate.

Referring again to FIG. 8, after the sensor 100 has been calibrated, thecircuit 160 calculates capacitance (820). To measure capacitance, thecircuit 160 may employ various processes. For example, the circuit 160may utilize a Schmitt-trigger along with a resistor to oscillate betweendigital logic levels (“0” and “1”) at a frequency directly related tothe sensed capacitance and the “RC time constant” created with the addedresistance. In this example, the oscillating signal serves as a clocksource for a counter. The difference in counter value is measured over aknown period of time (obtained from another time source), and the numberin the counter directly corresponds to the sensed capacitance.

In another example, the circuit 160 measures capacitance by introducinga transient input in voltage and/or current and then measuring theresponse to the transient input with respect to time. In this example,the circuit 160 calculates capacitance based on the measured responseand time.

The circuit 160 may calculate a change in capacitance by computing adifference between the measured capacitance and the baseline capacitancemeasured during calibration. The circuit 160 may use the change incapacitance to measure the movement of the sensed body near the sensor100.

After the circuit 160 calculates capacitance, the circuit 160 determinesan occupancy state and other movement-sensitive measurements (830). Forinstance, the circuit 160 may determine a binary occupancy state (e.g.,occupied or not occupied) based on the calculated capacitance and alsomay determine high precision, movement-sensitive measurements based onthe calculated capacitance. The circuit 160 may determine the highprecision, movement-sensitive measurements by translating the calculatedcapacitance to movement of the sensed body proximal to the sensor 100.The sensed movement may be processed to extract properties of the sensedbody such as breathing rate, sleep apnea, heart rate, or restlessness.The circuit 160 may calculate the movement-specific parameters on theprocessor 640.

The circuit 160 may use various processes to determine the binaryoccupancy state. For instance, the circuit 160 may detect occupancybased on measuring a capacitance greater than a threshold and detect alack of occupancy based on measuring a capacitance less than thethreshold. To reduce false activations or deactivations, the circuit 160may use the activation and deactivation thresholds described above tomanage small variations.

In addition to binary occupancy state, the circuit 160 may determine alocation of sensed objects relative to the sensor. In the implementationshown in FIG. 5 in which the sensor includes a cross-bar arrayconductive element pattern, the circuit 160 may determine an occupancystate applied at each row and column intersection across the sensor. Inthis regard, the circuit 160 may determine a two-dimensional grid thatrepresents occupancy state throughout the sensor for each frame. Withthe two-dimensional grid, the circuit 160 may detect which location ofthe sensor is being interacted with and monitor how that locationchanges over time.

The circuit 160 determines operational state of various components ofthe sensor 100 (840). For instance, the circuit 160 may determine abattery state of the circuit 160 battery. The circuit 160 also maydetect when various trouble conditions arise within the sensor 100(e.g., a connection to a conductive element of the sensor is lost). Thecircuit 160 may determine any measurable operational state of any of thecomponents of the sensor 100 or circuit 160 and use the one or moremeasured operational states to proactively address any detected troubleconditions or to attempt prevention of trouble conditions before theyarise.

The circuit 160 caches or stores data (850). For instance, the circuit160 may store values related to the calibration process, in addition tostate variables describing the sensor's operation state (e.g., batterystate, trouble conditions, etc.). The circuit 160 also may storemeasured capacitance values, determined occupancy states, and/or othermovement-specific measurements. The circuit 160 may store any datameasured or determined by the circuit 160. The storage may be temporaryand deleted after the data is transmitted to an external device.

The circuit 160 outputs data from the sensor 100 (860). For example, thecircuit 160 may communicate to a user or transmit to an external devicevalues related to the calibration process, in addition to statevariables describing the sensor's or circuit's operation state (e.g.,battery state, trouble conditions, etc.). The circuit 160 also maycommunicate to a user or transmit to an external device measuredcapacitance values, determined occupancy states, and/or othermovement-specific measurements. The circuit 160 may continuously orperiodically transmit data collected by the circuit 160. In someexamples, the circuit 160 may delay transmission until the storage onthe circuit 160 is nearly full (e.g., within a threshold storage amountof being full) and then transmit all of the stored data. In addition,the circuit 160 may transmit data upon request or may have rules thatdefine when data should be transmitted based on the values measured. Forinstance, the circuit 160 may transmit data to indicate a measuredcapacitance above a threshold value, a determined change in occupancystate, or a particular occupancy state that lasts more than a thresholdperiod of time. Any rules may be set to determine when the circuit 160transmits data and what data the circuit 160 transmits. For example, thecircuit 160 may predict occupancy states and only transmit measuredoccupancy states that differ from predicted states.

The described systems, methods, and techniques may be implemented indigital electronic circuitry, computer hardware, firmware, software, orin combinations of these elements. Apparatus implementing thesetechniques may include appropriate input and output devices, a computerprocessor, and a computer program product tangibly embodied in amachine-readable storage device for execution by a programmableprocessor. A process implementing these techniques may be performed by aprogrammable processor executing a program of instructions to performdesired functions by operating on input data and generating appropriateoutput. The techniques may be implemented in one or more computerprograms that are executable on a programmable system including at leastone programmable processor coupled to receive data and instructionsfrom, and to transmit data and instructions to, a data storage system,at least one input device, and at least one output device. Each computerprogram may be implemented in a high-level procedural or object-orientedprogramming language, or in assembly or machine language if desired; andin any case, the language may be a compiled or interpreted language.Suitable processors include, by way of example, both general and specialpurpose microprocessors. Generally, a processor will receiveinstructions and data from a read-only memory and/or a random accessmemory. Storage devices suitable for tangibly embodying computer programinstructions and data include all forms of non-volatile memory,including by way of example semiconductor memory devices, such asErasable Programmable Read-Only Memory (EPROM), Electrically ErasableProgrammable Read-Only Memory (EEPROM), and flash memory devices;magnetic disks such as internal hard disks and removable disks;magneto-optical disks; and Compact Disc Read-Only Memory (CD-ROM). Anyof the foregoing may be supplemented by, or incorporated in,specially-designed ASICs (application-specific integrated circuits).

It will be understood that various modifications may be made. Forexample, other useful implementations could be achieved if steps of thedisclosed techniques were performed in a different order and/or ifcomponents in the disclosed systems were combined in a different mannerand/or replaced or supplemented by other components. Accordingly, otherimplementations are within the scope of the disclosure.

What is claimed is:
 1. A movement-sensitive capacitive sensorcomprising: a first conductive element; a second conductive elementpositioned adjacent to the first conductive element to define acapacitive structure influenced by a sensed body within close proximityof the first conductive element and the second conductive element; afirst protective insulator; a second protective insulator sealed to thefirst protective insulator with the first conductive element and thesecond conductive element positioned between the first protectiveinsulator and the second protective insulator; and a circuit connectedto the first conductive element and the second conductive element, thecircuit being configured to: calculate, over time while a person isoccupying the movement-sensitive capacitive sensor and moving whileoccupying the movement-sensitive capacitive sensor, capacitance valuesbetween the first conductive element and the second conductive element,determining an average acquired signal in a current state by averaging,over a number of samples, values of measured capacitance between thefirst conductive element and the second conductive element; setting anactivation threshold based on the average acquired signal in the currentstate and a value that defines an amount of signal change required foractivation; setting a deactivation threshold based on the averageacquired signal in the current state and a value that defines an amountof signal change required for deactivation; after setting the activationthreshold and the deactivation threshold, monitoring a signalrepresentative of measured capacitance between the first conductiveelement and the second conductive element with respect to the activationthreshold and the deactivation threshold; based on the monitoring,determining that the signal representative of measured capacitancebetween the first conductive element and the second conductive elementhas crossed the activation threshold; based on the determination thatthe signal representative of measured capacitance between the firstconductive element and the second conductive element has crossed theactivation threshold, classifying the movement-sensitive capacitivesensor as in an occupied state; and transmit output that indicates thatthe movement-sensitive capacitive sensor is in an occupied state.
 2. Themovement-sensitive capacitive sensor of claim 1, wherein themovement-sensitive capacitive sensor has a flexible and fabric structurethat allows it to be utilized as an external sensor on existing beds andseats.
 3. The movement-sensitive capacitive sensor of claim 1, whereinthe movement-sensitive capacitive sensor has a flexible and fabricstructure that allows it to be integrated into a bed or seatconstruction.
 4. The movement-sensitive capacitive sensor of claim 1,wherein the first conductive element and the second conductive elementare patterned to increase sensing sensitivity.
 5. The movement-sensitivecapacitive sensor of claim 4, wherein the first conductive element andthe second conductive element have an interlocking comb-tooth conductiveelement pattern that increases sensitivity to movement on a surface ofthe movement-sensitive capacitive sensor.
 6. The movement-sensitivecapacitive sensor of claim 4, wherein the first conductive element andthe second conductive element have a cross-bar array conductive elementpattern that enables identification of a two-dimensional position of theperson on a surface of the movement-sensitive capacitive sensor.
 7. Themovement-sensitive capacitive sensor of claim 1, wherein the circuit isconfigured to determine the occupancy state of the movement-sensitivecapacitive sensor by detecting occupancy based on calculating acapacitance value that is greater than a threshold and detecting a lackof occupancy based on calculating a capacitance value that is less thanthe threshold.
 8. The movement-sensitive capacitive sensor of claim 1,wherein the circuit is configured to determine movement-sensitivemeasurements based on the calculated capacitance values by translatingthe calculated capacitance values to movement of the person proximal tothe movement-sensitive capacitive sensor.
 9. The movement-sensitivecapacitive sensor of claim 1, wherein the circuit is further configuredto determine the occupancy state of the movement-sensitive capacitivesensor by: based on detecting that the movement-sensitive capacitivesensor is in the occupied state, determining an average acquired signalin the occupied state by averaging, over the number of samples, valuesof measured capacitance between the first conductive element and thesecond conductive element; resetting the activation threshold based onthe average acquired signal in the occupied state and the value thatdefines the amount of signal change required for activation; resettingthe deactivation threshold based on the average acquired signal in theoccupied state and the value that defines the amount of signal changerequired for deactivation; after resetting the activation threshold andthe deactivation threshold, monitoring the signal representative ofmeasured capacitance between the first conductive element and the secondconductive element with respect to the reset activation threshold andthe reset deactivation threshold; based on the monitoring, determiningthat the signal representative of measured capacitance between the firstconductive element and the second conductive element has crossed thereset deactivation threshold; and based on the determination that thesignal representative of measured capacitance between the firstconductive element and the second conductive element has crossed thereset deactivation threshold, detecting that the movement-sensitivecapacitive sensor is in an unoccupied state.
 10. The movement-sensitivecapacitive sensor of claim 1, wherein the circuit is further configuredto determine the occupancy state of the movement-sensitive capacitivesensor by: based on detecting that the movement-sensitive capacitivesensor is in the occupied state, determining an average acquired signalin the occupied state by averaging, over the number of samples, valuesof measured capacitance between the first conductive element and thesecond conductive element; resetting the activation threshold based onthe average acquired signal in the occupied state and the value thatdefines the amount of signal change required for activation; resettingthe deactivation threshold based on the average acquired signal in theoccupied state and the value that defines the amount of signal changerequired for deactivation; after resetting the activation threshold andthe deactivation threshold, monitoring the signal representative ofmeasured capacitance between the first conductive element and the secondconductive element with respect to the reset activation threshold andthe reset deactivation threshold; based on the monitoring, determiningthat the signal representative of measured capacitance between the firstconductive element and the second conductive element has crossed thereset activation threshold; and based on the determination that thesignal representative of measured capacitance between the firstconductive element and the second conductive element has crossed thereset activation threshold, determining that the prior detection of themovement-sensitive capacitive sensor being in the occupied state wasincorrect and that the movement-sensitive capacitive sensor is now inthe occupied state.
 11. The movement-sensitive capacitive sensor ofclaim 1, wherein the circuit comprises a wireless radio configured totransmit the output wirelessly to a remote location.
 12. Themovement-sensitive capacitive sensor of claim 1, wherein the circuitincludes electronic storage configured to store data based on thedetermined occupancy state and the determined movement-sensitivemeasurements and the circuit is configured to transmit the output basedon the data stored in the electronic storage.
 13. The movement-sensitivecapacitive sensor of claim 1, wherein the circuit is connected to thefirst conductive element and the second conductive element viaconductive attachment points positioned on the first protectiveinsulator.
 14. The movement-sensitive capacitive sensor of claim 13,wherein the conductive attachment points include a first conductivefastener that provides a direct connection to the first conductiveelement and a second conductive fastener that provides a directconnection to the second conductive element.
 15. The movement-sensitivecapacitive sensor of claim 1, wherein the first protective insulator andthe second protective insulator include anti-microbial fabrics andsurfaces.
 16. The movement-sensitive capacitive sensor of claim 1,wherein the first protective insulator and the second protectiveinsulator include non-slip fabrics and surfaces.
 17. Themovement-sensitive capacitive sensor of claim 1, wherein the firstconductive element and the second conductive element are separatestructures from the first protective insulator and the second protectiveinsulator and the second protective insulator is sealed to the firstprotective insulator to encase the first conductive element and thesecond conductive element.
 18. The movement-sensitive capacitive sensorof claim 1, wherein the first conductive element and the secondconductive element are printed on an inner side of the second protectiveinsulator.
 19. The movement-sensitive capacitive sensor of claim 18,wherein the first conductive element and the second conductive elementcomprise conductive ink printed on the inner side of the secondprotective insulator.